I'm one of the Wagtail core developers. We made the mistake of spreading our support across too many channels (Google Groups, Stack Overflow, IRC, semi-private Slack) but we've made a clear decision to focus on Stack Overflow for developer-related questions:

https://stackoverflow.com/questions/tagged/wagtail

mainly as a result of this poll:

https://twitter.com/WagtailCMS/status/801384753589080064

Please feel free to contact me directly (details in profile) if you're not getting the support you need on SO.